(a) Field of the Invention
The present invention relates to an automatic transmission for a vehicle, and more particularly, to a planetary gear train of an automatic transmission for a vehicle that minimizes complexity, realizing at least ten forward speeds and at least one reverse speed, improves power delivery performance and fuel consumption by multi-stages of an automatic transmission, and improves driving stability of a vehicle by utilizing a low rotation speed of an engine.
(b) Description of the Related Art
Generally, in the field of an automatic transmission, a greater number of shift-stages provides technology for enhancement of fuel consumption and drivability of a vehicle. In particular, increases to the cost of oil has resulted in the requirement to enhance fuel consumption of a vehicle. In other words, research for an engine has been conducted to achieve weight reduction and to enhance fuel and research on an automatic transmission has been conducted to simultaneously provide better drivability and fuel consumption by achieving a greater number of shift stages.
For example to achieve more shift-stages for an automatic transmission, the number of components is typically increased, which may deteriorate installability, a production cost, weight and/or power flow efficiency. Therefore, to maximally enhance fuel consumption of an automatic transmission having more shift-stages, improved efficiency should include a smaller number of components.
Recently, an eight-speed automatic transmission has been introduced and a planetary gear train for an automatic transmission enabling more shift-stages is continuously required. An automatic transmission of eight or more shift-stages typically includes three to four planetary gear sets and five to six control elements (e.g., frictional elements). In other words, the total length may be increased and may cause a deterioration of installability. Further, disposing planetary gear sets in parallel or employing dog clutches instead of wet-type control elements has been attempted. However, such an arrangement may not be widely applicable, and using dog clutches may deteriorate shift-feel.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.